Machine-translated by Google. Questions are authored in English.
Top

Discussion

Knowing the fractional population of a two level system in thermal equilibrium at temperature T in a magnetic field \(\vec{B}\) , the magnetic moment is proportional to :

  • A.The difference between the population of the two states.
  • B.The sum of the population of the two states
  • C.Product of the population of the two states
  • D.Ratio of the population of the two states

Answer: A

The magnetic moment is proportional to the difference between the population of the two states.

In a two-level system, the states have moments \(+\mu\) and \(-\mu\) along \(\vec{B}\). With fractional populations \(n_{1}\) and \(n_{2}\), the net moment is \(\mu(n_{1} - n_{2})\), so it is set by the population difference, which the Boltzmann factor makes \(\tanh(\mu B/kT)\).

The sum of the fractional populations is always 1 and carries no information. The product and the ratio do not give the net moment directly.

No comment is present. Be the first to comment.
Loading…

Post your comment

Please log in or register to post a comment.